Hi Gene, I had one last year but think I tossed it in the fall
. You should be able to sub in any 12 volt single pole double throw relay with around 30 amp contacts. If its not charging then it may be the load resistor or the fuse (in a black box )next to it riveted to the rear of the converter section. Here is a link to a good troubleshooting guide magnatek
BTW if it is the resistor, I have a couple here that I can send you.